body{
    flex-direction: column;
}
// 头部
header{
    height: 44px;
    justify-content: center;
    align-items: center;
    text-align: center;
}
// 内容
main{
    background: url(../imgs/advertisement-bg.jpg) no-repeat 50%;
    background-size: cover;
}
.count-down{
    width: 106px;
    height: 40px;
    line-height: 40px;
    text-align: center;
    position: fixed;
    top: 74px;
    right: 10px;
    background-color: #fff;
    border-radius: 20px;
}
.slogan{
    width: 200px;
    position: fixed;
    bottom: 200px;
    font-size: 28px;
    left: 50%;
    color: white;
    font-weight: bold;
    transform: translateX(-50%);
    animation: slogan 3s forwards linear;
}
// 动画
@keyframes slogan{
    0%{
        opacity: 0;
        bottom: 200px;
    }
    50%{
        opacity: 0.5;
        transform: translateX(-50%) scale(1.5);
    }
    100%{
        opacity: 1;
        bottom: 100px;
        transform: translateX(-50%) scale(1.5);
    }
}